From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7BE99199E93; Thu, 6 Jun 2024 16:18:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=167.114.26.122 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717690685; cv=none; b=V4bhvn2XxX6HAsVureNKFANY3CQ1NmNzrryK1Au7eVUBERX2Qw74XWW0dyXn5ut1uGECLzMahuv+xncY3GleAzGY4PdPUfdj+a+cf8V/MGkyV/caXgfDAaxjhcDhCJz0W8ocsvBB2+PEmHm5/gREAaOoMIoWMou1utlXLihTjOY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717690685; c=relaxed/simple; bh=U270xwfQBOa8rfD5dC8oMKQewXsEPRNRTMtEy2i3IjY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lWGsq5BmAafj003bVGDN9xm8wKvNpTtRTRryQAkYvipYRlU5iupxieMJL8v2i0ep5M6wRIr++D8i1UG/0fpMJ83Gtj1lFuM+fsHWvxiWXVkbb71K4nOHg9Tkzc3FTztgcseV4m8uk0GdH+gceNL9KlSd3PPBjy4TOxNPRkJvlMA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=pX4M0HmK; arc=none smtp.client-ip=167.114.26.122 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="pX4M0HmK" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1717690682; bh=U270xwfQBOa8rfD5dC8oMKQewXsEPRNRTMtEy2i3IjY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=pX4M0HmKzr0UKZX1rLf3mSRWDLrb8555tuTQQSiqmT7ARgeLs9b2Mk7gVXzMtxGOF a8zrbTv0a6/LZfXaYCRUpwozK175er3RaoZNIeHBDZ9m1hyMct7JVKAIN5lSQMJZTR mBtcWcHb+zE6Zv7Ah2XhT49nRZDA0dPuDr2uR2wewskwaTDwPPMkHJrRf99oTmPYeG sdiMHwzVt6N2UiGFy5Nr7IguLh2kFBx896zCF9vkOM4yareTHVxOQOu2wcnjtVcQ4c P3ugiwnV1yFQVNjW1uDzAjBy2I9xUTtFz6+rTPmeyiArg2EcsgSHyDzegUNUIDd9Ij 79G/x/4PkLdfQ== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4Vw8d61MYFz13Gx; Thu, 6 Jun 2024 12:18:02 -0400 (EDT) Message-ID: Date: Thu, 6 Jun 2024 12:18:51 -0400 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] rust: add tracepoint support To: Boqun Feng Cc: Alice Ryhl , Steven Rostedt , Masami Hiramatsu , Peter Zijlstra , Josh Poimboeuf , Jason Baron , Ard Biesheuvel , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , linux-trace-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240606-tracepoint-v1-0-6551627bf51b@google.com> <20240606-tracepoint-v1-3-6551627bf51b@google.com> <389a8c55-a169-47ef-99c0-48f58003b40c@efficios.com> Content-Language: en-US From: Mathieu Desnoyers In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-06-06 11:49, Boqun Feng wrote: > On Thu, Jun 06, 2024 at 11:30:03AM -0400, Mathieu Desnoyers wrote: >> On 2024-06-06 11:05, Alice Ryhl wrote: >>> Make it possible to have Rust code call into tracepoints defined by C >>> code. It is still required that the tracepoint is declared in a C >>> header, and that this header is included in the input to bindgen. >>> >>> Signed-off-by: Alice Ryhl >> >> [...] >> >>> diff --git a/rust/helpers.c b/rust/helpers.c >>> index 2c37a0f5d7a8..0560cc2a512a 100644 >>> --- a/rust/helpers.c >>> +++ b/rust/helpers.c >>> @@ -165,6 +165,30 @@ rust_helper_krealloc(const void *objp, size_t new_size, gfp_t flags) >>> } >>> EXPORT_SYMBOL_GPL(rust_helper_krealloc); >>> +void rust_helper_preempt_enable_notrace(void) >>> +{ >>> + preempt_enable_notrace(); >>> +} >>> +EXPORT_SYMBOL_GPL(rust_helper_preempt_enable_notrace); >>> + >>> +void rust_helper_preempt_disable_notrace(void) >>> +{ >>> + preempt_disable_notrace(); >>> +} >>> +EXPORT_SYMBOL_GPL(rust_helper_preempt_disable_notrace); >>> + >>> +bool rust_helper_current_cpu_online(void) >>> +{ >>> + return cpu_online(raw_smp_processor_id()); >>> +} >>> +EXPORT_SYMBOL_GPL(rust_helper_current_cpu_online); >>> + >>> +void *rust_helper___rcu_dereference_raw(void **p) >>> +{ >>> + return rcu_dereference_raw(p); >>> +} >>> +EXPORT_SYMBOL_GPL(rust_helper___rcu_dereference_raw); >> >> Ouch. Doing a function call for each of those small operations will >> have a rather large performance impact when tracing is active. If it is > > Long-term plan is to 1) compile the C helpers in some IR and 2) inline > the helpers with Rust in IR-level, as what Gary has: > > https://lore.kernel.org/rust-for-linux/20240529202817.3641974-1-gary@garyguo.net/ > > and I use it for the upcoming atomic API support: > > https://github.com/fbq/linux/tree/dev/rust/atomic-rfc > > and it works very well. Thanks for the pointers, it makes sense. Thanks, Mathieu > > Regards, > Boqun > >> not possible to inline those in Rust, then implementing __DO_TRACE in >> a C function would at least allow Rust to only do a single call to C >> rather than go back and forth between Rust and C. >> >> What prevents inlining those helpers in Rust ? >> >> Thanks, >> >> Mathieu >> >> -- >> Mathieu Desnoyers >> EfficiOS Inc. >> https://www.efficios.com >> -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com